Designing a Carbon Fiber Bike

Editor’s Note: This is a guest blog post from John Nolin, who is a reseller at SolidXperts. He’s an avid bicyclist and uses Markforged parts to improve his bicycling experience.

Introduction

When I am not installing Markforged printers or teaching customers SOLIDWORKS, I do long distance charity rides. These are often 50, 75, or 100 miles in 1 or 2 days. In order to ride these distances, I need to have a bike that’s both comfortable and fast. My ride of choice is a short wheel base recumbent, the Vision R40. The short wheel base fits my frame better than a road bike and gives me an added layer of comfort during the long ride. However, increased comfort means increased weight. The R40 weighs 32 points, more than twice as much as a light road bike would. One of my favorite rides of the season is the Three Notch Century. Unfortunately the weight of the chromoly frame for my Vision R40 is less than ideal for the hill climbs through the New Hampshire White Mountains. A lighter bike could make a huge difference on these long, hilly rides.

A Homemade Carbon Fiber Bike

With the strong parts that Markforged printers can create, I realized that I could create a much lighter bike affordably. A complete replacement frame and seat assembly made of 3D printed components bonded between cut sections of carbon fiber tubing is a strong, manufacturable, and affordable frame. There are just 10 unique Onyx printed components in the final assembly and 7 different sections of pre-made, bicycle frame sized, carbon fiber tubing. Some parts and tubes are used in 2 – 4 different instances within the overall assembly. The front fork, stem, and handle bars have already been purchased from eBay in carbon composite. Material costs run at about $900, which more than a $1000 cheaper than a custom built composite frame. Couple that the ability to customize the design for myself, and you have a winning formula for a carbon fiber bike.

The First Part

Designing a composite bike frame is one thing; proving that it’ll be lighter and strong enough is a completely different story. In order to validate my design, I printed the first element of the new frame: a left rear dropout. This part holds the rear wheel in place, so it needs to be incredibly stiff. I designed it in Solidworks and uploaded it to Eiger. I decided to use Onyx material with a few layers of High Strength High Temperature Fiberglass reinforcement. The Onyx is tough and stiff and HSHT is strong, giving the part the characteristics that needed.

I printed the part on a Mark Two Enterprise kit printer. As printed, this frame component is just 26.7 grams. An equivalent metal component would be 115 grams or more. With this part, I know that the build is feasible and am pressing forward with fabrication.

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